This investigation will conduct a series of coordinated studies utilizing resistance hygrometry and partitional calorimetry to characterize and quantitate the thermoregulatory responses of the rhesus monkey (Macaca mulatta). It will evaluate this higher primate as a viable model for temperature regulation studies which cannot be performed in man. This investigation will specifically differentiate, and directly quantitate functional changes centrally, in the hypothalamic control centers and peripherally, at the level of the sweat gland of Macaca mulatta during heat acclimation, and correlate these changes with the increased thermoregulatory sweating capacity induced in this primate during heat acclimatization. It is signficant that the proposed investigation will provide basic data based on direct measurement of all necessary physiological parameters needed to construct a complete thermoregulatory profile for this higher primate. Such a model would be used to quantitate and differentiate the basic changes in thermoregulatory function in higher primates associated not only with the natural condition of heat acclimation but could also be used to study basic thermoregulatory malfunctions associated with disease conditions such as fever and heat stroke and may suggest better and more physiological methods of management and treatment of hyperthermic patients.